In the canon law of the Catholic Church, the computation of time,[1] also translated as the reckoning of time[2] (Latin:suppputatio temporis[2]), is the manner by which legally-specified periods of time are calculated according to the norm of the canons on the computation of time.

Months

Months are computed according to the calendar from the date of publication.[3] A "canonical month" (in contradistinction to a "calendar month") is a period of 30 days,[4] while a "calendar month" is a continuous month.

Vacatio legis

The vacatio legis is computed according to the calendar; for example, if a law is promulgated on 2 November, and the vacatio legis is 3 months, then the law takes effect on 2 February.[5] So a universal law has a vacatio legis of approximately 90 days—3 months taken according to the calendar—while a particular law has a vacatio legis of approximately 30 days—1 month taken according to the calendar—unless specified to the contrary.